Given the constraints of the 2012 regulations, it is clear that the optimal use of exhaust gasses is to blow them towards the outer edge of the diffuser to try to seal the diffuser from turbulent air created by the tyres.

This creates two engineering challenges given the specifics of the regulations which restricts the positioning of the exhausts.

As the exhaust exits have to be pointed 10-30 degrees upwards, the first challenge is to re-route the flow towards the floor. This isn?óÔé¼Ôäót too difficult to achieve ?óÔé¼ÔÇ£ by using cleverly-shaped bodywork it is possible to exert some control on the direction of the exhaust gasses.

The second problem is to ensure that as the exhaust gasses are dragged downwards the airflow around the sidepods isn’t affected in a negative way.

Ensuring that this airflow is funneled to the coke-bottle zone is a critical element of ensuring the diffuser works efficiently. This is because fast airflow over the rear of the car creates a low pressure zone above the diffuser exit and reduces the risk of airflow separation in the diffuser.

There are two solutions to the second problem. The first is the McLaren approach (which Ferrari adopted and McLaren introduced a further refinement of in Germany) whereby the exhausts jut out over the sidepod undercut so as not to interfere with the airflow.

The original tunnel was very square. Air entering the tunnel was at speed was forced back out as evidenced by Red Bull’s flow-vis tests.

The team abandoned this construction and went back to an earlier version of the sidepod/exhaust configuration. But thry did not give up on the concept and introduced a second version at Valencia:

There are a few obvious changes. The tunnel is larger and more rounded to ensure that the airflow doesn’t spill back out.

It also splits into two channels. The second, which can be seen just behind the first and closer to the rear of the sidepod, is smaller and slightly less rounded. Also there is no clear exit visible for either tunnel, unlike in the original version where the exit could be seen.

The third illustration shows a close-up of the two tunnels. Their different sizes and shapes are clearly visible. The key question is why are there two tunnels and where do they exit?

Air which enters the larger front tunnel exits inside the sidepod where it joins the air from the radiators and ultimately exits through a duct at the back of the car ?óÔé¼ÔÇ£ there is no aerodynamic benefit from this.

The second tunnel is fully ducted and blow into the hole for the engine’s starter motor, which is situated at the front of the diffuser. The benefit is that the high velocity air from the sidepod undercuts is channeled to where it is most effective.

This produce downforce and by directing the airflow in this precise fashion the downforce produced is more consistent, fixing a problem Sebastian Vettel complained about in earlier races.

The overall benefit from getting the exhausts to seal the outer edges of the diffuser is estimated to be two to three tenths of a second per lap, depending on the circuit.

There is debate as to whether the Red Bull or McLaren-style solution is more effective. Given how close the cars are in performance there doesn?óÔé¼Ôäót seem to be much in it.

However, what is apparent is that small tweaks in the sidepod/exhaust area can have a significant effect on performance ?óÔé¼ÔÇ£ witness McLaren?óÔé¼Ôäós resurgence in form since they introduced more deeply undercut sidepods in Germany. We can expect this area to remain a key focus of development during the rest of the season.

47 comments on Red Bull boost diffuser performance with twin tunnels

@infi24r
No.
He benefits from the blown diffuser in the same way that every other driver would.
On the other hand he has a genuine problem when the downforce isn’t consistent. A result of a primitive blown diffuser where the downforce over the rear will alter a lot whether you are off, or on throttle.
When RB introduced the retarded engine maps, the downforce became consistent, like had they just increased the seize of the rear wing, without anywhere near the same drag.
In other words, it made the car “normal” to drive again. Thats what he likes.

Last year Seb was much better than Mark at using the full potential of the hot blown diffuser. I believe that was a big factor in his dominant season. Its evident that with the FIA restrictions in this area, Webber is once again much closer to Seb’s pace (much like in 2010).

Seems Vettel is Button-kinda driver. If the car is in his smaller-then-for-other-top-drivers operating window, he can be as fast as the best of them, but as soon as the car needs just a little bit of taming, he becomes less then spectacular.

Brace, I would hardly compare him to Button. He was less-than-satisfied with the car in the opening rounds yet he managed to salvage a second, a probable 4th/3rd and a 5th (with a mediocre qualifying performance). Then Red Bull sorted it out partially and he won from pole. Whereas Button has only recently recaptured some form.

@infi24r – clearly you haven’t listened to any team radio’s this season: Button regularly complains of understeer, Vettel rarely. Although Button does have reason to complain: he performed very badly after China because the understeer was destroying his tyres.

Implanting such an exhaust solution always comes with disadvantages though. Lotus has a very tidy internal airflow and part of why the succeeded to do that was b/c of their conventional exhaust. Completely redesigning the sidepods mean rearranging the internal parts and thus messing with the internal airflow.

The only thing Red Bull seem to lack (as usual) is outright speed: a DDRS system similar to that of Lotus would be an elegant solution (and possibly necessary since the next two tracks are some of the highest speed on the calendar). I think it would be even more of an advantage for Red Bull the any other team.

@turbof1 – as @plushpile correctly pointed out, Red Bull have immense traction and plenty of downforce, so usually they run more aggressive set-ups and hence are slower in the speed traps: so a DDRS would be a massive gain for them (I’m sure Newey could come up with an ingenious system like that of Lotus’).

I’m also of the opinion that RBR has persevered with this concept mainly because Vettel seems to struggle without it. He’s not looked dominant when there’s not been some downforce-enhancing solution going on at the rear end… on the other hand, Webber seems to do best when there’s nothing fancy going on back there.
On another note, I’m waiting to see Vettel start from pole again: if he doesn’t pull out his usual few second lead over the first couple of laps, it’ll go some way to convincing me that RBR were in fact up to no good with their quick & easy ride height adjustments in parc ferme.

Thinking in wind-tunnel, stationary car terms: The layer of air next to the car is slowed by friction and is therefore less energetic for diffuser sealing purposes. Ducting this away enables the second tunnel to grab fast, smooth flowing air. It’s like sticking the second duct out into the full blowing breeze without it actually protruding, which would probably contravene a regulation.

Has everyone forgotten about allegations that Red Bull allegedly used a ride height system in the past (last year I think) that allowed the car to be as low to the ground as possible in qualifying but didn’t touch the ground when the car was filled with fuel?

@me262 – The only team that has cheated recently are McLaren when they stole Ferrari documents. Red Bull push the wording of the rules, as all great teams do. The reason they are double constructors champions is because they exploit the rules better than anyone else.

Before going for the big name, wasn’t there a more recent incident with Force India and use of aero information from another team last year?

Also while you are surveying from the moral high ground, perhaps you maybe able to clarify how Red Bull and their hand adjustable front suspension (which is ILLEGAL according to the FIA and had to be removed from the car) is ‘interpretting the rules’ rather than cheating?

The team had to remove it before the race, as it was not allowed under the rules and could have gotten them disqualified had they run it. Because it was not legal.
Its just that it was not noticed, or not followed up on, before Canada even if they (and/or others?) could have been using it before that.

That is because teams can show up with just about anything they like (if properly crash tested) before the race. And the FIA can look at parts and say some are not legal. Only the car they go into Parc Ferme with has to comply fully to the rules and would be punished if found to have something not OK on it (as happened to Sauber at Melbourne last year)

Not sure if anyone has seen this, but Steve Matchett (from SpeedTV) has a very interesting vidoe explanation on the Red Bull ‘sidepod tunnel’ configuration, with some very good photos to illustrate it: